The invention relates generally to multiple station forming machines for thermoformable panels and more particularly to a six station thermoforming machine having loading, heating, forming and unloading stations and a carousel for transporting thermoformable panels between such stations.
The technology of relatively large scale thermoforming of thermoplastic or thermosetting sheets has developed in response to continuing demands from various industries such as the automotive industry. Thermoformed panels are used as tonneau covers, floor panels, body panels, sound insulating partitions and the like in both motor vehicles and a wide variety of other products where relatively rigid, weather resistant, lightweight, tough, strong and non-rusting components are required.
The demand for such products has encouraged research and development of processes and manufacturing machines. One such machine is disclosed in U.S. Pat. No. 4,769,106, which is directed to an apparatus which assembles a pair of plastic sheets into a unitary device by welding about the peripheries of the sheets. The device includes a welding station, a cutting station and a conveying apparatus which transports the plastic sheets through the assembling stations. The conveying apparatus includes a moving carriage with grasping devices which engage the periphery of the plastic sheets. A cam arrangement operates to move the grasping devices from a first position in which they engage the plastic sheets to a second position in which the plastic sheets are released. Due to the linear construction of this machine and the use of a single device at each station, the overall maximum speed of the machine is limited by the maximum speed of the slowest station. This situation, which is a common manufacturing problem, adversely effects production efficiency.
A rotary thermoforming machine is disclosed in U.S. Pat. No. 4,555,377. In this machine, a rotating, substantially circular frame includes four sub frames having peripheral clamping members, which may be engaged or released to retain or release plastic sheets. The frame which carries the four carriages rotates and indexes them from a loading station through two heating stations to a mold station where the thermoformed product is produced.
A review of the foregoing two patent references as well as other references and prior art devices reveals that certain design choices and machine configurations limit production speed and interfere with both production throughput and product quality. The present invention is directed to an improvement in such thermoforming machines which address the foregoing and other shortcomings of the prior art.
A six station rotary thermoforming machine includes a carousel and a first loading station for first or upper panels, a second loading station for second or lower panels, two adjacent stations for heating the panels, a thermoforming station and an unloading station. The carousel includes a rotating circular frame which is driven by a centrally disposed drive assembly. The frame carries and supports six carrier frame assemblies having peripheral clamping members which receive panels of thermoformable material and rotate to sequentially move them from one station to the next. The two heating stations each include upper and lower radiant heaters. The thermoforming station includes a pair of opposed, vertically translatable platens which receive respective molds which engage and form the panels. Adjacent the thermoforming station is an insert or preform loader which places a preform into the mold during fabrication of the product. The number of stations and the residence time of the plastic panels to be formed in each optimizes production output of twin sheet thermoformed products.
Thus is an object of the present invention to provide a six station rotary thermoforming machine.
It is a further object of the present invention to provide a six station rotary thermoforming machine having two heating stations and one forming station.
It is a still further object of the present invention to provide a six station rotary thermoforming machine having two loading stations and one thermoforming station.
It is a still further object of the present invention to provide a six station rotary thermoforming machine having a carousel containing six panel engaging carrier frame assemblies and a centrally disposed drive unit.